This study extends currently ongoing research on both drinking and smoking (current Project 6) using ecological momentary assessment (EMA) to examine the use of alcohol with and without conjoint smoking to regulate emotions, and the effects of these regulation strategies on subsequent mood. We add a comparison group of Borderline Personality Disorder (BPD) patients. BPD exhibits high comorbidity with alcohol use disorders (AUDs) in both clinical and population-based samples. Cardinal symptoms of BPD, impulsivity and affective instability, are central constructs in theories of AUD etiology, so BPD represents a type of model system for studying the role of emotion regulation and disordered self-control in the genesis of AUD. We will collect EMA data from both random and event-based (e.g., drinking, smoking) assessments to address our aims. We will test the following hypotheses: (1) drinking episodes in BPD patients will be presaged by both positive and negative moods; drinking in non-affected controls (CON) will be presaged by positive but not negative moods; impulsivity will moderate these mood-substance use relations. (2) BPD patients' drinking episodes will be associated with heavier consumption (sex and body weight adjusted) than CON; group differences will be moderated by both affective instability and by impulsivity. Drinks consumed will be moderated by number of cigarettes in both groups. (3) Alcohol consumption's effect on mood will be characterized by both positive and negative reinforcement; smoking will attenuate the degree of reinforcement due to acute cross-tolerance effects in both groups. In BPD patients, underlying affective instability will attenuate the duration of alcohol-related, salutary effects on mood. (4) Negative post-drinking effects of alcohol on mood will be larger in BPD patients than controls because of additive effects of hedonic rebound effects of alcohol and negative affectivity in BPD patients; smoking will increase these effects in both groups. This study will provide important information about the role mood dysregulation plays in the etiology and maintenance of AUD, and how impulsivity and smoking may interact with mood dysregulation to lead to increased drinking. These results will have implications for both prevention and treatment of alcohol problems.